1. Field of the Invention
The present invention relates to a Light Emitting Diode (LED) package, and more particularly, a high power LED package designed to raise thermal radiation efficiency with a simplified structure in order to reduce the size and thickness thereof.
2. Description of the Related Art
LEDs are one type of semiconductors, and generate various colors of light when applied with voltage. When each LED generates light, its color is generally determined by chemical ingredients of the LED. Demand for the LEDs is continuously growing since the LEDs have various merits such as long lifetime, low drive voltage, excellent initial drive properties, high vibration resistance and high tolerance with respect to repeated power switching compared to lighting devices using filaments.
However, the LEDs also fail to convert electricity into light for 100%, thereby creating a considerable amount of heat. As a consequence, the LEDs adopt metal lead frames to radiate heat to the outside because internal components of the LEDs become stressed owing to their thermal expansion coefficient difference if heat is not properly dissipated.
In particular, some LEDs such as high power LEDs are recently adopted in illumination systems and backlight units for large-sized Liquid Crystal Displays (LCDs). Such high power LEDs are required to have superior thermal radiation performance because these systems or units require larger power.
FIG. 1 is a perspective sectional view of a conventional high power LED package. Referring to FIG. 1, the LED package 1 includes an LED chip 2 made of for example InGaN semiconductor, a metal slug 3 for seating the LED chip 2 thereon while functioning as heat guide means, a housing 4 for containing the metal slug 3, a silicone encapsulant 5 for sealing the LED chip 2 and the top of the metal slug 3, a plastic lens 6 for covering the silicon encapsulant 5, and a pair of wires 7 (only one is shown) for supplying voltage to the LED chip 2. In the meantime, the wires 7 are electrically connected with terminals 8. The LED chip 2 is connected to a submount by means of solders, and the submount seats the LED chip 2 on the metal slug 3.
Referring to FIG. 2, the LED package 1 of FIG. 1 is mounted on a board 10 of a heat sink, and a thermal conductive pad 9 such as solder is interposed between the metal slug 3 of the LED package 1 and the board 10 to facilitate the heat conduction between them.
The LED package 1 and its mounting structure on the board 10 as shown in FIGS. 1 and 2 are focused on thermal radiation to efficiently radiate heat to the outside. That is, the LED package 1 is so designed that the metal slug 3 as a heat sink is mounted directly or via the thermal conductive pad 9 on the board 10 in order to absorb heat generated from the LED chip 2 and radiate heat to the outside. Then, a major quantity of heat from the LED chip 2 flows through the metal slug 3 to the board 10 and only a minor quantity of heat is radiated to the air through the surface of the LED package 1 including the housing 4 and the lens 6.
Thanks to these reasons, LED packages of the above structure are widely adopted in the LED field.
However, the above conventional thermal radiation structure of the LED package has a bulky size thereby to obstruct the miniaturization of an illumination system. This structure is also complicated obstructing the automation of LED package production as well as requiring a large number of components to be assembled together thereby to burden manufacture cost.